Silicon carbide devices are advantageous in some applications over silicon devices due to the approximately 10× larger critical electric field strength of SiC over silicon. Also, the wide bandgap of SiC (3.2 eV) versus silicon (1.1 eV) allows SiC based devices to operate at much higher temperature than silicon devices. These properties are advantageous for applications requiring high-temperature and high-power.
Silicon carbide MOSFETs have been observed to be susceptible to Bias-Temperature Instability (BTI). Also, in SiC diodes and transistors, premature failure has been observed, particularly under voltage blocking conditions.
While not wishing to be bound by theory, the presence of chemical species may interact with the SiC electronic device to cause bias-temperature instability or premature device failure. Any changes in the concentration of the chemical species with operating condition, temperature or time can cause undesirable, unstable variations in their performance, or complete device failure.
Semiconductor devices are, by their nature, controlled by the presence or absence of mobile or stationary charges in the device. These charges can be located in the semiconductor or in other materials in the device such as metals or dielectrics. The charges may include donor and acceptor ions, electrons and holes, and other chemical species.
Semiconductor devices can be affected by chemical species that interact with the semiconductor to affect the device performance. This may include changes in the device parameters, such as leakage current, carrier lifetime, threshold voltage, blocking voltage, bipolar gain, channel mobility, and/or transconductance.
Semiconductor devices such as silicon MOSFETs or GaAs HEMTs have been demonstrated to be susceptible to the presence of chemical species in the device, such as hydrogen and/or water. Silicon carbide devices may also be susceptible to chemical species in the device, such as hydrogen and/or water or other species. Silicon carbide devices in structures such as bipolar transistors, IGBTs, MOSFETs, thyristors, JFETs, IGBTs and other electronic devices may be affected by these chemical species to affect the blocking voltage, gain, mobility, surface recombination velocity, carrier lifetime, oxide reliability, blocking voltage and other device parameters.
However due to the properties of SiC compared to silicon, SiC-based devices may be additionally susceptible to the influence of chemical species. Silicon carbide may be susceptible to the effects of these chemical species due to the much higher electric fields that are present in silicon carbide devices (in comparison to silicon and GaAs devices). Also, since SiC devices can operate at higher temperature (up to 500° C. or higher), operating at these temperatures may cause chemical species to be more reactive, have higher solubility and/or have increased diffusivity than devices that operate at lower temperature.
Accordingly, there still exists a need for semiconductor devices having improved device stability.